60.5 AC only devices60.5.1 A wiring device that is intended for use on alternating current circuits only shall be identified as such by means of the letters "AC", or "AC Only", or an acceptable frequency marking (for example, "60Hz"), or a phase marking, which shall be a part of the electrical rating. For multiphase devices that are intended for use only on a Wye system, the marking shall include the word "Wye," or the equivalent.